Sensors - an A to Z

By Aasha Bodhani

Published Monday, November 11, 2013

Sensor technology is now appearing everywhere, from kerbsides to kitchens, wheelie bins to robotic jellyfish – and sensors are increasingly proving themselves to be the critical interface between the virtual web and the Internet of Things.

Sensor technology has been around for many years, and has long been a critical component providing information for industrial processes, control and automation functionality, and many other sectors in engineering. Now sensors are key to just about every industrial market, from transport to telephony, and sensor technology can be found in anything from sprinklers to pacemakers.

Regardless of its application, the job of the sensor is to capture what is happening in the physical world and convert it into transmittable data. They typically operate by measuring and controlling data, such as light, heat, motion or pressure, which is converted into a signal and then sent to other wireless devices. There are of course many types of sensor and sensor technology, ranging from thermal, electromagnetic, mechanical, and motion sensors which are playing a major part in the creation of smart cities worldwide.

To convey an idea of the breadth of application requirement sensor technology is meeting, here we presents an A-Z of examples of how sensor technology is used to capture, test, control, and measure various spheres in all industry sectors.

Aerospace

Researchers at the University of Cambridge have developed a temperature sensor designed for jet engines that aims to improve efficiency, control, and safety of high-temperature engines. Accurate temperature readings are critical, as when the temperature becomes too high, the mechanical integrity of engine components are at risk, which can result in engine failure. The sensor consists of two bare wires of two different metals joined together at their ends, with a voltmeter incorporated into the circuit. The difference between the two ends of the thermocouple is measured by the voltmeter, and used to determine the temperature. Results from testing the prototype sensor have shown a reduction in drift by 80 per cent at temperatures of 1,200°C, and by 90 per cent at 1,300°C, potentially doubling the lifespan of engine components.

Beverage vending

Beverage vending machines are filled with motion sensors, enabling the machine to test temperatures, dispense drinks and food products, and also automatically alert the vendor when the machine needs restocking. In 2012, Coca-Cola implemented webcams and Microsoft's Kinect motion sensors – developed for gaming purposes – in its South Korean vending machines to get people to interact and dance for free bottles of Coca-Cola, in a bid to boost market profile.

Crops

Flood-plain ecosystems support wide ranges of vegetation, but can be sensitive to changes in the hydrological cycle. Researchers at the University of Reading project FUSE (Floodplain Underground SEnsors) inserted wireless networking sensors underground at Oxford Meadows in order to measure the variables that control plant health and composition, including soil moisture, groundwater level, soil chemistry, and temperature. The data may be used to improve our flood-plain ecosystem understanding. Other crop-management sensor solutions report on soil aridity to see if the soil is dry enough to require irrigation.

Disease detection

Researchers from the physics and biology departments at the University of Pennsylvania joined forces to build a Lyme disease detector using a carbon nanotube sensor. Lyme disease is a bacterial infection that humans contract via infected ticks, which, if not detected early, can cause nerve damage. The two-stage treatment begins with an ELISA examination, where antibodies are used to identify substances; however, this can occasionally produce false positives. For greater accuracy, the research team grew a large array of carbon nanotubes to use as sensors, and attached antibody proteins to the nanotubes. The antibodies attract and capture a type of protein found in the flagellum of bacteria that are the source of Lyme disease. The protein causes a change in how well the nanotube sensors are able to conduct electricity, therefore by measuring voltage, the researchers can determine if the bacteria are present in blood.

Earthquakes

Scientists, Antonino D'Alessandro and Giuseppe D'Anna from the National Institute of Geophysics and Volcanology have discovered tiny sensors that can detect which way a handset is facing and orientate the screen accordingly. It can also detect strong vibration, similar to earthquakes. The pair used the LIS331DLH Micro Electro-Mechanical Systems (MEMS) chip, and compared it with the earthquake sensor EpiSensor EST force balance accelerometer: they found the chip managed to pick-up earthquake vibrations greater than Magnitude Five on the Richter scale. Another prototype solution from IBM uses data generated by vibration sensors (MEMS accelerometers) within data-centre server hard-drives to quickly analyse and assess information generated by seismic events. This technique is enabled by collecting hard-drive sensor data and transmitting it via high-speed networks to a data processing and classification centre.

Forest fires

Sensors manufacturer Libelium's environmental protection projects covered 210 hectares in northern Spain, with the aim of providing an environmental monitoring infrastructure to deliver fire early-warning signals. The system's three focal components include the wireless sensor, communication network, and the reception centre; additionally, 90 sensor 'waspmotes' are deployed in strategic locations to measure the temperature, humidity, carbon monoxide, and carbon dioxide every five minutes, and then wirelessly communicate readings to a reception centre. Other gases detected include methane, ammonia, ethanol, toluene and nitrogen dioxide. When not in use the waspmotes – powered with solar-rechargeable batteries – 'hibernate' to save battery life, and are powered with rechargeable batteries and a solar panel.

Greenhouses

An automated greenhouse can improve crop management by monitoring the temperature, light and humidity levels: this can be measured accurately by placing temperature and humidity sensors in line with the growing tip of the crop. Typically greenhouses are fitted with a heater, sprinkler system, and window and door monitor, all linked to a computer. If one acts abnormally the computer can activate the temperature and humidity sensor to control the heater and sprinkler system. Raspberry Pi and Arduino have jointly created 'iStoof', the system is driven by Raspberry Pi and Arduino microcontrollers which automates greenhouses. The system can control and monitor any greenhouse, using temperature, humidity, light intensity, radiation, and wind pH sensors.

Health

The University of Edinburgh's 'Implantable Microsystems for Personalised Anti-Cancer Therapy' (IMPACT) project aims to examine and analyse cancerous tumours with the use of tiny sensors. The miniature chips will be designed to measure vital factors about the tumour, such as the levels of blood oxygen and biological molecules, this information is then transmitted wirelessly to medical staff. These readings will enable to the doctor to target stubborn areas of the tumour which required intensified radiotherapy, and will be able to foresee if treatment is working. The five-year £5.2m project, funded by the Engineering and Physical Sciences Research Council, will involve producing new sensors and miniaturising existing sensors.

Internet search

Computer scientists at Glasgow University are designing a search engine that will obtain results from sensors in the physical world. The 'Search engine for MultimediA Environment geneRated content' (SMART) project enables Internet users to search and analyse data from net-connected sensors such as Webcams and Net-connected microphones. By matching search queries with sensor information, and cross-referencing data from social networks, users will be able to receive detailed responses to questions such as "What part of the city hosts live music events which my friends have been to recently?" or "How busy is the city centre?" The SMART project is a joint research initiative between the University of Glasgow, Atos, Athens Information Technology, IBM Haifa Research Lab, Imperial College London, City of Santander, PRISA Digital, Telesto, and Consorzio S3 Log.

Jellyfish

A large autonomous sensor-equipped robotic jellyfish, dubbed Cyro, has been built by researchers from the College of Engineering at Virginia Polytechnic Institute and State University – Virginia Tech. The project aims to develop self-powered, self-guided devices for surveillance and environmental monitoring, as well as studying aquatic wildlife, mapping ocean floors, and monitoring currents. The robot measures 1.7m long, weighs 77kg and is powered by a rechargeable nickel-metal hydride battery that gives the jellyfish five hours of continuous swim time. Cyro's 'skin' is dressed in a thick layer of silicone laid over a bowl-shaped cover to mimic a real-life jellyfish body. To create the hydrodynamic movement, the mechanical arms use electric motors to control the motion and the implementation of on-board sensors capture, store, analyse and communicate sensory data. The $5m project is funded by the US Naval Undersea Warfare Centre and the Office of Naval Research.

Kitchens

Homes are getting smarter: from motion sensor lights and smoke detectors to temperature and humidity sensors. Within this scenario the kitchen is undergoing most transformation. Standard kitchen appliances have become smart, such as sensor-integrated dustbins, soap dispensers, smart fridges and smart drawers. Scientists and language experts at Newcastle University have incorporated sensors which provide cooking instructions in French. Digital sensors are built into utensils, ingredient containers, and other kitchen equipment which communicate with a tablet or laptop PC to provide instructions and feedback if the user goes makes a wrong move. Other kitchen appliances are also now greatly integrated with a variety of sensors: for instance, AEG's 'Lavamat', a washing machine with a load sensor. The sensor assesses the weight of the wash load and recommends the right amount detergent dosage required for the wash.

Lighting

Lighting company EnLight's DolFin (Digital Optical Light Fully Integrated Network) is an intelligent light-sensing and Wi-Fi communications system enabling two-way and real-time light monitoring by detecting ambient light and automatically calculating a daylight profile. The DolFin light sensor has GPS built in, which automatically switches lamps on at present times, and then dims them by 30 per cent between 12.30am to 6.00am.

Medical devices

The health industry's ongoing digital makeover aims to deliver e-health strategies including electronic patient files, machine-to-machine (M2M) applications, mobile health aids, and 'virtual health carers', with the aim to treat long-term medical conditions. Product development company Sagentia has developed an iPhone app for medical sensor company Senseonics' Glucose Monitoring System which is to be connected using Bluetooth Low Energy connectivity. It consists of an implanted micro-sensor, a wireless transmitter that communicates with the sensor and a smartphone app. After an insertion in the skin, a patient's glucose levels can be measured every few minutes with results of hyperglycaemia and hypoglycaemia automatically sent to the patient and the doctor.

NFC payment

Near-field communication (NFC) technology has existed for almost a decade, but banks and mobile operators are now implementing it into payment processes. The short-range wireless communication technology is placed in two electronic devices to enable small amounts of data to be exchanged over short distances. NFC-equipped phones are made with a chip and an inbuilt coil of wire and the contactless payment reader, which also has an inbuilt coil of wire, generates a magnetic field. When the smartphone is waved or tapped close to the reader, electric currents jump between the coils of wire which signals data-carrying radio waves between the devices. Mobile vendors such as HTC, Samsung, Google (via Motorola), and LG have manufactured NFC-enabled handsets; additionally credit-card companies have issued NFC-enabled credit cards, including MasterCard's PayPass and Visa's PayWave.

Odour

Environmental monitoring technology start-up AirBase Systems has launched CanarIT – an air quality sensor device capable of monitoring odour. CanarIT provides real-time measurements of odour in ambient air, and makers claim it can also detect environmental hazards. The odour module is regulated against the European Odour Unit concentration scale, based on the response to 40ppb of n-butanol as defined in EN 13725. It uses nanotechnology sensors with Internet connectivity (Wi-Fi or GSM) to deliver air-quality data to its AirBase data cloud. The data is then made available on the Internet or as a subscription alert service to mobile phones, for use by municipalities, community groups, and citizen scientists, say.

Parking

A pilot street-parking scheme in Birmingham's Jewellery Quarter was launched earlier this year, with the aim of helping motorists find available spaces and relieving traffic congestion. Amey, the city's road maintenance contractor, partnered with Birmingham City Council, and embedded around 200 small sensors to identify the presence of a parked vehicle; this data is then presented via the 'Parker' smartphone app or website, which motorists can check in advance or in real time.

Quantum-cascade laser

Military and security services have been looking to sensor technology to find tell-tale chemicals that indicate whether the barrel on the battlezone roadside is an empty container – or something more deadly. Lasers make it possible to bounce light off a target from a distance and analyse the reflected spectrum. Most lasers produce a fixed frequency of light, but the quantum cascade laser can sweep through a range of wavelengths. Current designs are able to work in the near-infrared and terahertz region. A number of R&D teams in this field have focused on the mid-infrared region of the electromagnetic spectrum because it can provide much information about chemical composition. Many common bonds found in organic chemicals vibrate in the mid-infrared region, absorbing the radiation strongly at specific frequencies. The 'fingerprint region' (covering wavelengths from 5m to 20m) usefully pinpoints specific chemicals – such as explosives – because each one has a specific absorption profile. To identify chemicals, software fits the data from a sensor that receives the reflected or transmitted light to those molecules' predicted absorption curves, so that it won't trigger if a similar gas is picked up.

Radiation monitoring

The meltdown of the Fukushima nuclear power plant in 2011 resulted in the release of radioactive material which left the majority of northern Japan contaminated with an unknown amount of radioactivity. Residents in Japan say the government and the power utility have provided little information concerning the levels of radiation. For this reason citizen Pieter Franken set up cross-border non-profit organisation Safecast. Days after the explosion, Safecast distributed Geiger counters to residents in the fall-out zone to enable them to monitor radiation levels; however, the counters sold out. Safecast volunteers built its own device dubbed 'bGeiger' which takes radiation readings every five seconds. The device is strapped into a car and using GPS technology the data is linked to build radiation maps which are transferred online.

Sport

Researchers at Loughborough University have developed movement tracking and sensor technologies to help swimmers improve performance. The sensors wirelessly generate data on the swimmer's body position, speed and acceleration and enables coaches to advise on performance. The device is a lightweight box containing tiny accelerometers and gyroscopes sensors which is fitted to the small of a swimmer's back. Force transducers are incorporated into the starting blocks and pressure sensors into the touch pads at the end of the swimming lanes. As the swimmer moves, the sensor captures the movement and sends the data to a laptop PC, where the coach and examines the swimmers performance. The system was developed by Loughborough University's Sport Technology Institute in conjunction with British Swimming, and funding from Engineering and Physical Sciences Research Council.

Traffic

One of the UK's busiest highways, the A14, which connects the container port at Felixstowe to Birmingham, is to become Britain's first Internet-connected road. The pilot project funded by BT, the Department for Transport and Cambridge technology vendor Neul, will see the 50-mile stretch be placed with a network of sensors which will, at first, monitor traffic, reduce congestion, and improve road safety. The OFCOM-approved trial will exploit unused frequencies between television channels, known as 'white space', for communication. The project aims to enable the sensors to connect to mobile phones, levy tolls, or direct cars along diverted routes and even manage speed.

Underground

In 2010 Transport for London awarded a Costain and Laing O'Rourke joint venture with £300m for the redevelopment of Bond Street Underground Station. London Underground has an ongoing issue with underground water eroding soil and creating cavities; therefore, while grouting work was taking place as part of the makeover, Wireless Remote Condition Monitoring tunnelling and geo-technical Senceive placed over 100 deployable/re-deployable FlatMEsh tilt wireless sensors on patented magnetic brackets attached to tunnel segments, to detect tiny levels of movement and deformation in the tunnel lining in real time. Senceive is involved in a tunnel relining project, between Bond Street and Baker Street stations.

Vehicle accident

A European initiative, eCall, is intended to offer rapid assistance to motorists involved in an accident and reduce emergency response times anywhere in the European Union. In the event of a severe crash, an eCall-equipped vehicle will automatically trigger an emergency call to '112'. Even if the vehicle's occupants are unable to speak, data regarding the incident will be sent to the emergency services including the exact location of the accident using GPS and mobile communication services. The European Commission has proposed legislation to ensure that from October 2015, all new models of passenger vehicles would be fitted with eCall technology, and that emergency call response centres have the correct infrastructure to handle eCalls.

Waste management

According to the Department for Environment, Food and Rural Affairs, the UK generates roughly 177 million tonnes of waste every year, much of which is due to poor use of resources. Though the amount of waste is high, not every household or business/industrial premises produces the same amount of waste over a given period, which means waste-management companies could be collecting half-empty dustbins and using resources unnecessarily, while collection costs (e.g. vehicle fuel) continue to rise. The solution lies in sensors, claims waste management logistics company Enevo: its 'One Collect' is a method to monitor the amount of waste in a dustbin. A small battery-powered wireless sensor is attached to the underside of the lids, and monitors different types of waste, such as paper, glass, metals, and liquids, and the fill level in real-time. The data, including, alerts for abnormal events (such as high temperatures and movement and predicted fill-up dates) is communicated back to the Enevo servers, and, once analysed, it is displayed on the Enevo One Collect Website for analysis.

Xbox 360

Gaming no longer involves sitting in one spot and relying on the fingers and thumbs to play: now full-body movement is required as Nintendo's Wii console and Microsoft's Xbox Kinect have integrated sensors giving players the ability to convert their bodies into a game controller. The Xbox Kinect, in particular, scans the layout of the room and configures play space; it then captures 48 points on the player's body creating a digital form by gathering data on user's body, such as height, body shape, and gender, and transformed into a 3D avatar shape.

Yachts

German telecommunications company Fraunhofer Heinrich Hertz Institute has developed a sensor system that identifies critical weak points in yachts, and relays the information to crew members before they turn into major faults and breaks. The system operates by using Fibre Bragg Grating (FBG) sensors; these are inscribed in optical fibre and are attached to the sail, hull, or mast. As the yacht is in motion, it has an expanding or contracting effect on the FBG causing the light transported in the fibre optical cables to strike different sensors.

Zebras

Nasa scientists are studying zebra migration to understand precisely where they go when, and also whether migration is a genetically programmed behaviour or if external influences are a factor. By combining GPS tracking and Nasa's satellite technology, zebra movement can be recorded, alongside environmental conditions, which will enable scientists to see if vegetation is a fundamental reason for zebra migration. Though tracking animal movement with satellite technology is not groundbreaking, the project is connected to Nasa environmental satellites that monitor vegetation growth and rainfall, so a bigger picture of the zebra's circumstances can be built up.